(A) Field of the Invention
The instant invention relates to a foundation for a mast, in particular a steel tube mast, supporting pillar, rails, heavy construction machinery, and the like, comprising a ground anchoring portion of hollow section design which is open at its bottom and comprises, at its top, a connecting member for the mast or the like.
(B) Description of the Prior Art
Such a foundation is known, for example, from U.S. Pat. No. 1,784,568 which suggests that a releasable flange connection be provided between telephone poles and the like and the end of an anchoring portion set in concrete in the ground and being of tubular of H section. The anchoring of the tubular or H section member in the ground is effected by first excavating the ground at the place where the telephone pole is to be erected, subsequently the anchoring portion is secured in the hole in the ground, and finally concrete is poured into the hole to fill the same.
It is evident that the known solution requires a lot of material as well as time. And with greater foundations additional casing and supporting work is needed in the excavation to prevent any undesired break-in of earth which would pose constant danger to the construction workers who are fixing the anchoring portion in the hole. Besides, earth moving equipment (excavators) and concrete mixers etc. must be available to reduce the known solution to practice.
A very great disadvantage of the known solution is presented by the fact that the natural stability of the ground is destroyed by having to dig a hole for the construction of the foundation described. This lost stability essentially can be compensated only by an increased amount of concrete.
The solution known from U.S. Pat. No. 1,784,568 is not suited either for constructing the foundations of supporting pillars of large erecting shops and the like, the bottom of which is to be covered with asphalt or concrete upon levelling of the ground. With the known solution, the asphalt or concrete covering of the shop floor practically cannot be applied before the foundations for the supporting pillars are finished. This has the consequence that the work involved cannot be accomplished by means of large equipment alone but, in addition, requires small implements to be used in the direct vicinity of the foundations already constructed. Otherwise the concrete or asphalt floor could be provided only incompletely in the area of the foundations set, and subsequent manual work would be indispensable.
Swiss Pat. No. 589,772 discloses a tubular anchoring portion for steel masts and the like. This anchoring portion is driven into the ground and comprises an outer collar (flange) to provide increased lateral stability and lies on the surface of the ground when the anchoring portion is sunk into place. The drive-in of the tubular anchoring portion is facilitated by the lower end thereof being provided with a closed tip.
It is a disadvantage of this known solution that the tubular anchoring portion must be relatively slender in shape so as to keep the resistance against its being driven into the ground with reasonable limits. And yet the earth resistance cone is very high so that, consequently, strong forces must act on the anchoring portion in order to drive it into the ground. Usually this is accomplished by means of a drop hammer or ram. The risk of breakage of the anchoring portion is increased with this method. Furthermore, it cannot be avoided that the hole in the ground resulting from those impacts is beaten out or enlarged laterally, a circumstance which of necessity reduces the stability. This is the reason why the outer collar mentioned above is needed which has a much greater outer diameter as compared to the tubular anchoring portion. It is only by virtue of this overdimensioned outer collar that sufficient laterial stability is obtained.
The situation is similar to Swiss Pat. No. 589,772 with the solution proposed in 1899 in British Pat. No. 6349, leaving aside the fact that the latter comprises no separate anchoring portion, at the upper end of which the mast proper is fixed. Instead, the lower end of the mast has a tip, and an outer collar in the form of an annular or similar flange is provided spaced from the lower end of the mast. It is extremely complicated to drive the known mast into the ground. Practically, it can be done only with relatively short masts. With longer masts more expensive "digging in" cannot be avoided.
Finally, it is known from German utility model 1 964 445 to slip a mast of steel or aluminum sheet into a tubular ground anchoring member made of concrete or plastics and having previously been dug into the ground. The stability of this type of mast anchoring is very limited and, at best, sufficient for light masts of sheet material. The solution known from German utility model 1 964 445 is utterly unsuitable as the foundation of supporting columns of erecting shops or bridge piers.